DESORIPTIOKS OP SPECIES. 299 



Seminula humilis Girty?. 



1899. Seminula humilk. Girty, U. S. Geol. Surv., Mon., vol. 82, pt. 2, p. 565, pi. 71, figs. 6a-6c. 

 Madison limestone: Yellowstone National Park. 



The impression upon which White based his determination of Seminula sub- 

 tilita"- in the fauna from Larimer County is a small, nearly circular shell, having a 

 diameter of 11 mm., which probablj' represents a dorsal valve of a specimen belong- 

 ing to the genus Semimda. The beak is small, depressed, and incurved, and neither 

 fold nor sinus is developed. This impression agrees very closely with dorsal valves 

 of the little shell which I described under the name of S. hiwiilis. At the same time 

 it can not be distinguished from dorsal valves of the same dimensions of the type 

 which, in the Perry Park and Leadville regions, 1 have referred to Seminula sub- 

 qiiadrata. While it shows no evidence of a fold, in them also that feature of the 

 dorsal valve is less noticeable than the corresponding one of the ventral, and it is 

 propoi-tionally obscure in young specimens; and doubtless immature shells of some 

 of the numerous varieties of Seminula siiMilita assume the same form, but certainly 

 it is very different from the common mature type of .S. Hubtilita. 



Locality and h-orizo-n. — Pebbles of Millsap limestone (?) in the Red Beds con- 

 glomerate, Larimer County (station 2364). 



Seminula sp. 



In the San Juan region a single tiny Seminula has been collected. Its entire 

 length is but 6 mm., and Ijecause of its probable immaturity and its solitary occur- 

 I'ence it has scarcely seemed worthy of more than mention, without an attempt to 

 refer it to any described .species. 



Locality and horizon. — San Juan region (station 2381); Ouray limestone. 



CRANiENA Hall and Clarke, 1893. 



Cran^na subelliptica var. hardingensis n. var. 



PI. I, figs. 8-10. 



As Hall and Clarke figure but do not describe Cranxna nvhelliptica., the following 

 description, based upon a series of upward of 50 specimens from the type locality, 

 Sciotoville, Ohio, may not be without value: 



Shell large, ovate. Outline regular. Curvature evenly rotund, without fold 

 or sinus. Shell substance thick, abundantly punctate. Surface marked by numer- 

 ous, more or less distinct growth lines. 



Oransana subellijjtica is difficult to describe effectually because it is largely 

 lacking in distinctive characters. While in shape it is always longer than wide, 



nU. S, Geol. Geog. Surv Terr., Bull., vol 5, 1879, p. 215. 



